An integrate study for mapping the dampness distribution on wall paintings

Dampness is a major cause of decay to porous materials such as stone, brick, mortar and plaster as shown in the scientific literature of the conservation science. Accurate diagnosis of the cause and extent of damp is a fundamental step for preserving wall paintings. Nevertheless, the moisture distribution within a wall painting is difficult to determine. This paper shows the study performed on the frescoes in S. Rocco, Cornaredo (Milan, Italy). The church is seriously affected by moisture diffusion which causes damage to the frescoed surfaces. In this work the monitoring of dampness in the wall painting of this church has been performed using an integrated approach of unilateral NMR and IR Thermography (IRT), supported by the traditional gravimetric methods. The unilateral NMR technology is fully portable and can be directly applied in situ, without any sampling. In this study the results obtained by this portable and non invasive NMR technique are related to the results obtained with two conventional techniques used to detect and measure the dampness: the gravimetric methods and IRT. IRT is a noncontact, ND test that uses an infrared camera to detect and record infrared energy producing a thermal image of the object’s surface temperature. Current IRT procedures do not easily supply quantitative data of the water content, only the qualitative approach can be extensively applied. The simplest solution of quantifying moisture consists in the integration of IRT with the direct measurements of water provided by other testing, such as weighting tests, moisture probes, etc.